Fig. 2

psoriasis keratinocytes display partial EMT and invasive behavior.

(a,b) Stills from in vivo time-lapse recordings (Videos 1 and 2) of clones of membrane-bound GFP-labelled (Tg(Ola.Actb:Hsa.hras-egfp)) basal keratinocytes in a mosaic wt (a) or an atp1b1a morphant (b) embryo; ′n min′ indicates elapsed time since the start of the recordings at 48 hpf (Videos 1 and 2). Wild-type cells form a rigid epithelium and maintain their shapes and relative positions (a), whereas atp1b1a morphant cells form cellular processes (arrows), dynamically dis- and re-associate (arrowheads) and eventually crawl on top of each other (cell 1; b, first panel). Cell 1 moves out of the focal plane after 60 min, cell 6 changes its shape from roundish to more hexagonal and vice versa. Scale bars: 20 µm. (c,d) Transverse TEM sections through median fin fold, at 58 hpf. In wt (c), an intact basement membrane (BM; black arrowhead) separates the compact layer of basal cells from the underlying dermis, which contains actinotrichia (small asterisks). The psoriasis mutant (d) displays large intercellular gaps (large asterisk) between basal cells, cellular protrusions (arrows) of basal cells, a discontinued BM (arrowheads to remaining BM), direct contacts between epidermal cells, and disassembling dermal actinotrichia (small asterisks) that lose their regular shape and striated pattern. bc: basal cells; pc: peridermal cell. Scale bars: 1 µm. (e,f) Laminin and peridermal-specific GFP double IF, counterstained with DAPI, at 58 hpf. Transverse sections through the fin fold of Tg(krt4:GFP) transgenics reveal basement membrane fragmentation (arrowhead) below an epidermal aggregate in the mutant (f). (g,h) Laminin and type II collagen double IF, counterstained with DAPI at 58 hpf; view of fin folds of whole mounts, showing basement membrane fragmentation and actinotrichia disassembly in the mutant (h). (i,j) Laminin and p63 double IF, counterstained with DAPI at 58 hpf; transverse section through the yolk sac. Arrowheads in (j) point to holes in the basement membrane of the mutant. Note the presence of p63 keratinocytes below the basement membrane in the dermal space. Scale bar: 20 µm.